Buggy code:
public class PhoneticEngine { static final class PhonemeBuilder { public static PhoneticEngine . PhonemeBuilder empty ( Languages . LanguageSet languages ) { } private final Set < Rule . Phoneme > phonemes ; private PhonemeBuilder ( Set < Rule . Phoneme > phonemes ) { } public PhoneticEngine . PhonemeBuilder append ( CharSequence str ) { } public PhoneticEngine . PhonemeBuilder apply ( Rule . PhonemeExpr phonemeExpr ) { } public Set < Rule . Phoneme > getPhonemes ( ) { } public String makeString ( ) { } } private static final class RulesApplication { private final List < Rule > finalRules ; private final CharSequence input ; private PhoneticEngine . PhonemeBuilder phonemeBuilder ; private int i ; private boolean found ; public RulesApplication ( List < Rule > finalRules , CharSequence input , PhoneticEngine . PhonemeBuilder phonemeBuilder , int i ) { } public int getI ( ) { } public PhoneticEngine . PhonemeBuilder getPhonemeBuilder ( ) { } public PhoneticEngine . RulesApplication invoke ( ) { } public boolean isFound ( ) { } } private static final Map < NameType , Set < String > > NAME_PREFIXES = new EnumMap < NameType , Set < String > > ( NameType . class ) ; private static CharSequence cacheSubSequence ( final CharSequence cached ) { } private static String join ( Iterable < String > strings , String sep ) { } private final Lang lang ; private final NameType nameType ; private final RuleType ruleType ; private final boolean concat ; public PhoneticEngine ( NameType nameType , RuleType ruleType , boolean concat ) { } private PhoneticEngine . PhonemeBuilder applyFinalRules ( PhoneticEngine . PhonemeBuilder phonemeBuilder , List < Rule > finalRules ) { if ( finalRules == null ) { throw new NullPointerException ( "finalRules<seq2seq4repair_space>can<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; } if ( finalRules . isEmpty ( ) ) { return phonemeBuilder ; } <START_BUG> Set < Rule . Phoneme > phonemes = new TreeSet < Rule . Phoneme > ( ) ; <END_BUG> for ( Rule . Phoneme phoneme : phonemeBuilder . getPhonemes ( ) ) { PhoneticEngine . PhonemeBuilder subBuilder = PhoneticEngine . PhonemeBuilder . empty ( phoneme . getLanguages ( ) ) ; CharSequence phonemeText = PhoneticEngine . cacheSubSequence ( phoneme . getPhonemeText ( ) ) ; for ( int i = 0 ; i < ( phonemeText . length ( ) ) ; ) { PhoneticEngine . RulesApplication rulesApplication = new PhoneticEngine . RulesApplication ( finalRules , phonemeText , subBuilder , i ) . invoke ( ) ; boolean found = rulesApplication . isFound ( ) ; subBuilder = rulesApplication . getPhonemeBuilder ( ) ; if ( ! found ) { subBuilder = subBuilder . append ( phonemeText . subSequence ( i , ( i + 1 ) ) ) ; } i = rulesApplication . getI ( ) ; } phonemes . addAll ( subBuilder . getPhonemes ( ) ) ; } return new PhoneticEngine . PhonemeBuilder ( phonemes ) ; } public String encode ( String input ) { } public String encode ( String input , final Languages . LanguageSet languageSet ) { } public Lang getLang ( ) { } public NameType getNameType ( ) { } public RuleType getRuleType ( ) { } public boolean isConcat ( ) { } }

Fix:
Set < Rule . Phoneme > phonemes = new TreeSet < Rule . Phoneme > ( Rule . Phoneme . COMPARATOR ) ;